diff --git a/activerecord-sqlserver-adapter.gemspec b/activerecord-sqlserver-adapter.gemspec
index 56542b42d..bc1705683 100644
--- a/activerecord-sqlserver-adapter.gemspec
+++ b/activerecord-sqlserver-adapter.gemspec
@@ -16,6 +16,6 @@ Gem::Specification.new do |s|
   s.require_path  = 'lib'
   s.rubyforge_project = 'activerecord-sqlserver-adapter'
   
-  s.add_dependency('activerecord', '4')
+  s.add_dependency('activerecord', '~> 4.0.0')
 end